Psychotic disorders distort a person's perception of reality. Schizophrenia is a particularly severe type of psychotic disorder and is characterized by persistent defects in a patient's perception or expression of reality. Approximately one percent of the population develops schizophrenia during their lifetime. More than two million Americans suffer from the illness in a given year.
A person experiencing untreated schizophrenia typically demonstrates grossly disorganized thinking and may also experience delusions or auditory hallucinations. Although the illness primarily affects cognition, it can also contribute to chronic problems with behavior or emotions.
There is no objective biological test for schizophrenia, though studies suggest that genetics and biochemistry are important contributing factors. Current research into the development of the disorder often focuses on the role of neurobiology, although an identifiable biological cause has not been found.
Hence, diagnosis of schizophrenia is based on the self-reported experiences of the patient, in combination with secondary signs observed by a psychiatrist or other competent clinician. The most commonly used criteria for diagnosing schizophrenia are from the American Psychiatric Association's Diagnostic and Statistical Manual of Mental Disorders (DSM) and the World Health Organization's International Statistical Classification of Diseases and Related Health Problems (ICD).
According to the DSM, to be diagnosed as having schizophrenia, a patient must display two or more of the following symptoms for a significant portion of time during a one-month period: delusions, hallucinations, disorganized speech (e.g., frequent derailment or incoherence, speaking in the abstract), grossly disorganized behavior (e.g., dressing inappropriately, crying frequently), or such negative symptoms as lack or decline in emotional response, lack or decline in speech, or lack or decline in motivation, where a negative symptom is defined as a decline in, or lack of a, normal behavior. In addition, the patient must show significant social and/or occupational dysfunction as a result of these symptoms.
Many hypotheses have been formulated as to the cause of schizophrenia. For example, infections (e.g., a slow virus), genetic disorders, autoimmune or immune dysfunctions, and environmental factors have all been advanced as possible causes of schizophrenia. The effectiveness of the neuroleptic drugs, which block dopamine as a transmitter, has led to the hypothesis that schizophrenia is the result of dysfunction of neurons utilizing dopamine as a neurotransmitter. In particular, some studies have hypothesized that there is an over activity in these neurons which utilize dopamine. However, recent studies have questioned the dopamine hypothesis because there is little evidence of elevated dopamine levels in many schizophrenic patients.
Other biochemical hypotheses have been put forward to explain the causes of schizophrenia. For example, newer medications that are a combination of dopamine receptor and serotonin receptor antagonists have been found to be equally or more effective than previously used dopamine antagonists, suggesting that excess serotonin may also play a role in schizophrenia.
Treatment options for patients suffering from schizophrenia and other psychotic disorders are limited. Although a cure for psychotic disorders does not currently exist, several antipsychotic drugs are available that may improve or stabilize symptoms for some patients. However, many of these drugs have undesirable side effects as they pass through the body to the brain after being taken orally or injected intravenously. Psychotherapy (e.g., cognitive behavioral therapy) or other forms of talk therapy may also be used to treat schizophrenia and other psychotic disorders. However, such psychotherapy usually only focuses on the direct reduction of the symptoms, such as issues of self-esteem, social functioning, and insight.